Damper

ABSTRACT

A damper assembly constructed to close a flue pipe for a burner during non-use of the burner and to automatically open prior to burner ignition. An actuator operated by a thermo-statically controlled heater and an expansible fluid, rotates a baffle of the damper assembly to open the flue pipe. A safety interlock requires the baffle to be opened before the burner is ignited. When the burner is turned off, the actuator delays closing of the baffle for a time to allow exhausting of residual combustion products. In one embodiment, two baffles are operated to close a flue pipe above and below a draft diverter.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to automatically operated dampers for burnerflues.

2. Prior Art.

The typical flue from the burner of a hot water tank or furnacecontinually provides a free path for the flow of waste products ofcombustion. As a result, residual heat is lost from the heat exchangerby the stack effect of the flue, due to the continued flow of ambientair that enters the burner area and leaves through the stack aftercombustion has stopped. In addition, heat from the water in a hot watertank is lost to cooler air flowing through the portion of the flue thatextends up the center of the tank. Moreover, a hot water tank fluetypically has a draft diverter that, while limiting the stack effect orupward flow through the central flue of the tank, allows air to be drawnfrom the room, and ambient heat is lost through the flue. As a result ofheat loss from furnaces and hot water tanks, fuel requirements areincreased and the efficiency of operation is decreased. Suchinefficiencies and the loss of heated room air has become a seriousproblem with the shortages and high cost of fuels.

Draft retarders are known for use in flues of heating systems. Forexample, U.S. Pat. No. 3,934,796 shows a solenoid operated damperenergized by a heating system for automatic operation in a flue of thesystem. U.S. Pat. No. 3,010,451 shows a smoke pipe damper controlled byan electrically operated hydraulic motor. Other examples ofautomatically operated dampers are shown by U.S. Pat. Nos. 3,396,777 and2,508,885. These arrangements utilize actuators that havedisadvantageous characteristics and lack safety features and otheradvantages of the present invention, and fail to prevent heat lossassociated with draft diverters.

SUMMARY OF THE INVENTION

The present invention provides in one embodiment a damper assembly foran uninterrupted flue, such as a furnace flue, and in another embodimentprovides a damper assembly for use with a draft diverter, as typicallyused with hot water heaters. The damper assembly of the presentinvention provides a baffle or baffles that are spring biased closed andoperated through linkages by a thermostatically controlled actuator toopen an associated flue. Importantly, the actuator is energized withoutsparking or arcing, which is dangerous in an environment where fuelfumes may exist, and operates with a slow rather than snap action, toavoid noise and stress upon operating linkages. The operation of theactuator, when closing the baffle, includes a delay to allow combustionproducts to be drafted out of the burner for a period of time sufficientto eliminate the trapping of smoke or fumes.

More specifically, a cylinder and piston type actuator is used tooperate the baffle or baffles of the damper assembly, the piston beingfluid operated to extend a rod by the vaporization of a fluid, such asFreon, by a thermostatically controlled heater. The piston is springreturned when the heater is deactivated and the vaporized gas condenses.This construction provides an inherent delay in operation and a gradualmovement during actuation.

A safety interlock is provided to assure that the burner with which thedamper assembly is used does not operate with the baffle closed. This isachieved by a switch operated when the baffle is moved between openedand closed positions and which prevents the supplying of fuel to theburner until the baffle is open.

A further safety feature is achieved from the use of the heat-operatedactuator by locating the actuator directly adjacent the flue that isbaffled. In the event of a build up of heat in the burner and flue areadue, for example, to the starting of the burner (for example, due to agas leak or failure of the fuel valves upstream of the burner) withoutthe damper or dampers being opened, a dangerous situation would result.However, as heat builds up, the temperature of the actuator rises,causing the expansible fluid within the actuator to expand and open thebaffle or baffles without actuation through the thermostaticallycontrolled electrical system.

With the present invention installed on a furnace flue, a single baffleretards loss of heat from the heat exchanger of the furnace after burneroperation. This allows the blower of the furnace to circulate theresidual heat in the furnace throughout the heating system without lossto air drafted through the furnace flue. The baffle also prevents flowof furnace room air through the furnace flue.

With the present invention in use with a draft diverter, as with a hotwater heater, two baffles are operated by the same actuator to close theflue above and below the draft diverter. Convective air flow through thelower flue that extends through the center of the hot water tank isprevented, retarding loss of heat that otherwise occurs from the heatedwater to the flow of air. Closing of the upper flue prevents the flow ofroom air through the draft diverter and up the flue pipe. The damper ofthe present invention, thus, provides a safe and effective way toautomatically prevent the loss of heat through burner flues.

The above and other features and advantages of the present inventionwill become better understood from the detailed description thatfollows, when considered in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front elevational view, with parts in section, of a damperassembly embodying the present invention, in which two baffles areprovided for a draft diverter of the type used with hot water heaters;

FIG. 2 is a side elevational view of the damper assembly of FIG. 1; and

FIG. 3 is a diagrammatic showing of a control system for a hot waterheater utilizing the damper shown in FIGS. 1 and 2, for automaticallycontrolling the baffles.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

With reference to FIGS. 1 and 2 of the drawings, a water heater 10 isindicated in phantom, with a damper assembly 12 that embodies thepresent invention. The damper assembly is incorporated into a draftdiverter 14 connected in a flue pipe 16 of the hot water heater. Thelower part 16a of the flue pipe extends through the center of the hotwater tank from a burner below. An upper part 16b extends from the topof the damper assembly 12.

The draft diverter 14 includes a lower mounting piece 18 that fits overthe flue portion 16a , and an upper hood 20 riveted to a collar 22 thatconnects to the upper part 16b of the flue pipe 16. The hood 20 providesa passage from the lower flue pipe 15a to the upper pipe 16b and alsoprovides a communication through its lower opening 20a from the ambientatmosphere to the flue 16.

The damper assembly 12 includes two circular baffles, a lower baffle 24within the mounting piece 18 and an upper baffle 26 within the collar22. The lower baffle is supported on a shaft 28 by a screw 30. The shaftis journaled in openings 32, 33 (FIG. 2) in the mounting piece. Theupper baffle is supported on a shaft 36 by a screw 38. The shaft isjournaled for rotation in openings 40, 41 in the collar 22.

The shaft 28 extends laterally through the hood 20 and the extending endsupports a wheel sector 44. The shaft 36 extends laterally in the samedirection as the lower shaft, and supports a wheel sector 46 on theextending end. Both sectors function as bell crank levers to rotate therespective shafts 28, 36.

An actuator 50 and a linkage 52 are carried by a support bracket 54mounted to the hood 20 for rotating the shafts 28, 36 to move thebaffles between opened and closed positions.

The actuating linkage 52 includes an arm 56 pivoted at one end by ascrew 58 to the bracket 54. The arm carries links 60, 62 on oppositesides, secured by a cross pin 64. The link 60 extends downwardly to thesector 44, where it is pivotally secured by a screw 66. The link 62extends upward from the arm to the sector 46, where it is pivotallysecured by a screw 68.

A coil spring 70 encircles the shaft 28 adjacent the wheel sector 44.One end of the spring is secured to the bracket 54 and the other end tothe sector 44 by a stud 72. The spring biases the sector and hence thelinkage 52 and thus both shafts 28, 36 in a direction (indicated byarrows in FIG. 1) that rotates the baffles 24, 26 to an open position,as shown in phantom in FIG. 1. Thus, in the event of a failure linkage52, the baffles will be biased open.

The actuator 50 is adjustably held by a clamp 76 bolted to the bracket54. The actuator has an extensible rod 78 pivotably secured to the arm56 by a pin 80 intermediate the pivot screw 58 and cross pin 64. Theactuator is comprised of an electrical heater 82 in the end adjacent thebracket 76, and a chamber 84 in which a piston 86 on the rod 78 moves.An internal compression spring 88 biases the rod 78 into the actuatorbody. An expansible fluid, such as Freon that will readily vaporize withheat, is in the chamber 84 and serves to move the rod 78 outward whenthe heater 82 is energized, to pivot the arm 56 from the solid positionshown in FIG. 1 to the phantom position. Pivoting of the arm moves thelinks 60, 62 and pivots the baffles 24, 26 from the solid line positionto the phantom line position of FIG. 1. A particularly suitable actuator50 is the Gould refrigerant actuator manufactured by Gould Inc.

A microswitch 90 is secured to the bracket 54 in a position to beactuated by movement of the arm 56. The microswitch is a part of asafety interlock for the operation of the burner of the hot water tank,so the burner will not operate when the baffles 24, 26 are closed.

A control system for the operation of the damper assembly 12 when usedwith a hot water heater is shown in FIG. 3. A fuel line 96 isdiagrammatically shown extending from a source of fuel 98, such as a gasmain, to a gas burner 100 of the hot water heater. The fuel lineincludes a first thermostat-operated gas valve 102, a pressure-operatedelectric switch 104 downstream from the gas valve 102, and asolenoid-actuated second gas valve 106 downstream from thepressure-operated electric switch. The first gas valve 102 is connectedto and operated by the thermostat of the hot water heater and is openedwhen the thermostat indicates the temperature of the water in the tankis below a certain level. The valve closes when the water has beenheated to a desired level. The pressure operated switch 104 is connectedin series with a 24 volt power transformer 108 and the heater 84 of theactuator 50 through electrical lines L1, L2, L3, L4 and L5. Thetransformer 108 is connected directly to a 110 volt AC source. When thefirst gas valve 102 is opened by the hot water tank thermostat, thepressure operated switch 104 is closed by virtue of the increase in fuelpressure, and causes the heater 84 of the actuator 50 to heat theexpansible fluid, which expands to extend the rod 78, swinging thebaffles 24, 26 to their opened positions.

The solenoid of the second gas valve 106 is connected in series with thetransformer 108 and the microswitch 90 through lines L6, L7, L8, L9 andL5. When the arm 56 reaches the phantom position shown in FIG. 1 throughoperation of the actuator 50, the microswitch 90 is closed and thesolenoid of the second gas valve 106 is actuated to open the valve toallow fuel to flow to the burner 100, which is pilot-operated andignites. Thus, only after the baffles 24, 26 have been moved to theiropen position can the burner receive fuel. It will also be apparent thatif for some reason the actuator 50 fails while the burner is operatedand closes the baffles, the switch 90 will be deactuated, closing thegas valve 106, shutting off the burner 100.

When the thermostat of the hot water heater indicates that thetemperature of the water has reached the desired level, the first gasvalve 102 is closed, stopping the supply of fuel to the burner 100. Thepressure operated switch 104 senses the decrease in fuel pressure andopens the electrical circuit to the heater 82 of the actuator and theexpansible fluid in the actuator cools. During the time of cooling, thebaffles 24, 26 initially remain open and then gradually close, whileresidual products of combustion escape through the flue. In the case ofgas burners, approximately 25 seconds is allowed for closing, to provideadequate time for the products of combustion to vent from the burner andthe hot water tank flue portion 16a. In the case of a system using anoil burner, a longer delay is established, on the order of 21/2 minutes,because oil has a smoldering effect that requires longer to exhaust theresidual products of combustion.

Once the burner has turned off and the baffles have closed, furtherdraft through the flue pipe 16 is prevented and loss of heat from thehot water due to convection through the flue pipe 16a and loss ofambient heat from the surrounding area through the hood 20a isprevented.

The construction of the actuator 50 provides a safety feature inaddition to those described above, because of the heat responsiveoperation of the actuator and the location proximate to the flue. In theevent of a buildup of heat in the flue, due to an improper operation ofthe burner by a flow of fuel under pressure insufficient to operate thepressure switch 104, as by a relatively slow leak through the gasvalves, and thus without actuating the heater 82 of the actuator, thedampers 24, 26 would not be open and a dangerous situation would result.However, the buildup of heat in the flue would be sensed by theactuator, causing the expansible fluid within the actuator to expand andopen the baffles.

It will be apparent from the description of the actuator and itsoperation that the extension of the rod 78 is gradual so as not tostress the parts, and is quiet. There are no contacts or spark gapsassociated with the actuator that might result in sparking, as forexample with an electric motor, and the actuator is therefore safe in anenvironment where there may be combustible fumes.

In the event a draft diverter is not used with the burner, as is thecase with most furnaces, it will be readily apparent that the hood 20,collar 22 and the upper baffle 26 and associated link 62 can be omittedwithout changing the remaining structure or operation.

By way of example to illustrate the effectiveness of the presentinvention in saving fuel, a hot water heater was tested by filling theheater with water and keeping it to its heated condition without drawingwater. For a five day period, without the damper assembly 12 in place,158 cubic feet of gas was used as fuel to maintain the temperature ofthe tank. With the damper assembly 12 installed, and the remainingconditions being essentially the same (with obvious minor changes inenvironmental conditions) 51 cubic feed of gas was used for a five dayperiod to maintain the temperature of the water. With the damperassembly in place, the water heater burner did not turn on during thefive day period in which there was no use of the water in the tank.Rather, the heat from the pilot light kept the water hot for the testperiod of time. Without the damper assembly, it was necessary for theburner to operate intermittently to maintain the temperature.

While a preferred embodiment of the invention has been described indetail, it will be apparent that modifications or alterations may bemade therein without departing from the spirit and scope of theinvention set forth in the appended claims.

What is claimed is:
 1. A damper assembly comprising:a baffle pivotablysupported for movement between two positions; an actuator for pivotingthe baffle, said actuator having a heater, an expansible fluidundergoing a fluid to vapor expansion phase change during heating and avapor to fluid contraction phase change during cooling and a membermovable in response to expansion and contraction of said fluid; alinkage between said movable member and the baffle to pivot the bafflebetween said two positions in response to movement of said actuatormember and a switch located to be actuated in response to movement ofsaid movable member, so its conductive condition is responsive to theposition of the baffle.
 2. A damper assembly and safety interlock foruse with a flue of a fuel burner, comprising:a conduit portion to form apart of said flue; a baffle pivotably supported in said portion formovement between a position where it closes the portion and a positionwhere the portion is open; an actuator for pivoting the baffle, saidactuator having a heater, an expansible fluid undergoing a fluid tovapor expansion phase change during heating and a vapor to fluidcontraction phase change during cooling and a member movable in responseto expansion and contraction of said fluid; means supporting theactuator adjacent said conduit portion; a linkage between said movablemember and the baffle to pivot the baffle between said two positions inresponse to movement of said actuator member; a switch operable betweenconductive and nonconductive modes in response to operation of theactuator; and a fuel valve for supplying fuel to said fuel burner, saidfuel valve being operable to supply fuel only when said switch is in oneof its said modes.
 3. A damper assembly, fuel supply system and safetyinterlock for a thermostat-controlled fuel burner having a flue,comprising:a conduit portion to form a part of said flue; a bafflepivotably supported in said portion for movement between a positionwhere it closes the portion and a position where the portion is open; anactuator for pivoting the baffle, said actuator having a heater, anexpansible fluid undergoing a fluid to vapor expansion phase changeduring heating and a vapor to fluid contraction phase change duringcooling and a member movable in response to expansion and contraction ofsaid fluid, and arranged to move said baffle toward the position wherethe portion is open when the actuator is operated; means supporting theactuator adjacent said conduit portion; a linkage between said movablemember and the baffle to pivot the baffle between said two positions inresponse to movement of said actuator member; a first switch operablebetween conductive and nonconductive modes in response to operation ofthe actuator; a thermostat-operated first fuel valve in a fuel linebetween a source of fuel and the burner, operable to open and close tocontrol flow of fuel through the line in response to conditions of thethermostat; a pressure-operated second switch operable betweenelectrically conductive and nonconductive modes in response to pressurein said fuel line between the fuel valve and the burner to electricallyenergize the actuator heater; whereby the burner is operable only whenthe actuator is energized and the baffle remains in an open position. 4.A damper assembly as set forth in claim 3 wherein said actuator remainsactuated for a predetermined time after energizing current to theactuator and fuel to the burner are discontinued, whereby the baffleremains open for a predetermined time after the thermostat-operatedfirst fuel valve is closed and burner operation has stopped.
 5. A damperassembly comprising:two baffles arranged in series, each pivotablysupported for movement between two positions; an actuator for pivotingboth baffles concurrently, said actuator having a heater, an expansiblefluid undergoing a fluid to vapor expansion phase change during heatingand a vapor to fluid contraction phase change during cooling and amember movable in response to expansion and contraction of said fluid; alinkage between said movable member and both baffles to pivot thebaffles together between said two positions in response to movement ofsaid actuator member; and a switch located to be actuated by movement ofsaid movable member, so its conductive condition is responsive to theposition of the baffles.
 6. A damper assembly and safety interlock foruse with a flue of a fuel burning, comprising:a conduit portion to formpart of said flue, said conduit portion having an opening intermediateits ends for entry of ambient air; two baffles one before and one aftersaid opening, each pivotably supported in said portion for movementbetween a position where it closes the portion and a position where theportion is open; an actuator for pivoting both baffles concurrently,said actuator having a heater, an expansible fluid undergoing a fluid tovapor expansion phase change during heating and a vapor to fluidcontraction phase change during cooling and a member movable in responseto expansion and contraction of said fluid; means supporting theactuator adjacent said conduit portions; a linkage between said movablemember and the baffles to pivot the baffles together between said twopositions in response to movement of said actuator member; a switchoperable between conductive and nonconductive modes in response tooperation of the actuator; and a fuel valve for supplying fuel to saidfuel burner, said fuel valve being operable to supply fuel only whensaid switch is in one of its said modes.
 7. A damper assembly, fuelsupply system and safety interlock for a thermostat-controlled fuelburner having a flue, comprising:a conduit portion to form a part ofsaid flue, said conduit portion having an opening intermediate its endsfor entry of ambient air; two baffles, one before and one after saidopening, each pivotably supported in said portion for movement between aposition where it closes the portion and a position where the portion isopen; an actuator for pivoting both baffles concurrently, said actuatorhaving a heater, an expansible fluid undergoing a fluid to vaporexpansion phase change during heating and a vapor to fluid contractionphase change during cooling, and a member movable in response toexpansion and contraction of said fluid, and arranged to move saidbaffles toward the position where the portion is open when the actuatoris operated; means supporting the actuator adjacent said conduitportion; a linkage between said movable member and both baffles to pivotthe baffles between said two positions in response to movement of saidactuator member; a first switch operable between conductive andnonconductive modes in response to operation of the actuator; athermostat-operated first fuel valve in a fuel line between a source offuel and the burner, operable to open and close to control flow of fuelthrough the line in response to conditions of the thermostat; apressure-operated second switch operable between electrically conductiveand nonconductive modes in response to pressure in said fuel linebetween the fuel valve and the burner to electrically energize theactuator heater; and a second fuel valve in the fuel line between theburner and the location in the fuel line where the pressure is sensed bythe pressure-operated switch, said second fuel valve being operableelectrically in response to actuation of said first switch when thebaffles are moved to positions where the conduit portion is open toallow flow of fuel to the burner; whereby the burner is operable onlywhen the actuator is energized and the baffles remain in open positions.8. A damper assembly as set forth in claim 7 wherein said actuatorremains actuated for a predetermined time after energizing current tothe actuator and fuel to the burner are discontinued, whereby thebaffles remain open for a predetermined time after thethermostat-operated first fuel valve is closed and burner operation hasstopped.